Polyethylene (PE), in particular linear low density polyethylene (LLDPE), films are widely used for packaging products, for example foodstuffs, liquids (e.g. detergent refills), etc. In such uses, the sealing properties of the film are particularly important. To address this, it is known to incorporate a comonomer in the PE in order to provide a lower melting point component in the polymer and so increase the hot tack property of the film. In this regard, it is known that incorporation of a hexene-ethylene copolymer in the LLDPE provides superior sealing properties to an LLDPE incorporating a butene-ethylene copolymer and that incorporation of an octene-ethylene copolymer provides superior properties to an LLDPE incorporating a hexene-ethylene copolymer.
The use of higher α-olefin comonomers, i.e. C4 or greater α-olefins, however increases the cost of the polymer product and, generally, the efficiency of comonomer incorporation decreases as the carbon content of the comonomer increases, i.e. hexene is less efficiently incorporated than butene and octene is less efficiently incorporated than hexene, etc.
We have now surprisingly found that by incorporating two different α-olefin comonomers a polyethylene film product may be produced which has superior sealing properties to the polyethylenes produced using either of the comonomers as the sole comonomer.